"I like the special sea floor grade because you can use a gravel vac on it. Calcium carbonate binds phosphates, so the cleaner you keep it, the less change of free phosphates in your tank. I personally never used to touch it.....it worked for a while....then my phosphates climed. Cleaned half of the sand bed at a time with three weeks in between cleanings (so you dont wipe out micro organisms that stir sand) i havent had a problem since. :) Thats why i like this grade of sand, it can be vacumed up with a gravel vac and not lose sand in your siphon."

It's much more complex then that...Calcium carbonate will bind phosphates with a high PH, if your ph drops though, phosphates will be dissolved from the substarates and make it back into the water. Also you vac your sand ? How deep is your sand ? < Thats not really a good idea.If you manage the sandbed corectly and your water flow over the bed, there should be no reason for the bed to be touched.

Ryan.. add your rock first..as much as you can afford..if adding later make sure its cycled .

remember too that sand beds house bacteria.....when bacteria digest they digest with acid, acid in turn digests if you will sand, which is why sand beds disolve over time. Theres a whole phosphate cycle, see link at bottom.

here is an exerpt ( Likewise, phosphate can precipitate onto the surface of calcium carbonate, such as onto live rock and sand. The absorption of phosphate from seawater onto aragonite is pH dependent, with the maximum binding taking place around pH 8.4 and with less binding at lower and higher pH values. If the calcium carbonate crystal is static (not growing), then this process is reversible, and the aragonite can act as a reservoir for phosphate. This reservoir can make it difficult to completely remove excess phosphate from a tank that has experienced very high phosphate levels, and may permit algae to continue to thrive despite cutting off all external phosphate sources. In such cases, removal of the substrate may even be required.)

Phosphates in the ocean are .002 ppm......if your reef tank is at that....im a monkeys uncle. in our reef tanks we over feed. One feeding of 5 grams in a 100 gallon tank brings your phosphates to 0.4 ppm which is enough to inhibit your growth of sps corals....where does this phosphate go? Your rocks, and your sand bind the free phosphates for later use by other organisms, including bacteria.

The key is to not introduce phosphates to your sand in the first place. Which is why i clean my sand bed. I have almost 60x turnover in my tank.....not much settles in my sand bed....but its better to get it out, then to let it sit....rot and be absorbed by the sand to be released at a later date. IMO, sand beds that are left unattended are ticking time bombs.

http://www.advancedaquarist.com/issues/ ... 2/chem.htm

I prefer not to follow the crowd. What im doing is working for me....my growth is insane, my colors are outragious, and I just morphed a zoanthid thats black and pink. Im happy and so are my corals.